This invention relates generally to sheet registration and clamping apparatus, and more particularly, to apparatus which sequentially registers a sheet at a registration location, clamps such sheet at such location, and guides such sheet as it is moved from such location.
In certain reproduction apparatus, such as printers or duplicators, copies of information are reproduced on cut sheets of paper. Typically, the paper sheets are fed seriatim to a support where they are registered and clamped to the support. The support retains the sheet in its registered location while an operation is carried out on such sheet. For example, the support may be moved into engagement with a printing platen where marking particles or ink, in an imagewise pattern corresponding to information to be reproduced, are transferred to the sheet. The sheet is thereafter transported from the support to apparatus for fixing the transferred pattern to the sheet to form the desired reproduction.
Prior reproduction apparatus employ many different mechanisms for registering and clamping a sheet to the support. Most commonly, the mechanisms include a plurality of clamps mounted on the support, each clamp having a registration portion and a portion extending from the registration portion in a direction upstream of the travel of a sheet toward the registration portion. As a sheet is registered against the registration portions, the extending portions are moved to clamp the lead edge of the registered sheet between such extending portions and the support. Such mechanisms are generally effective to carry out their intended registration and clamping functions. However, if there is significant curl in the lead edge of a sheet being registered, the extending portions of the mechanisms can interfere with movement of the sheet toward the registration portions. Moreover, the lead edge of a registered sheet must somehow be lifted over the extending portions on transport of the sheet away from the mechanism after the work operation (e.g., image transfer) is performed on the registered sheet.